In order to promote a better understanding of the subject invention as alluded to in the Abstract it is deemed beneficial to present a background of information in order that the attributes or advantages of the improved impeller can be compared with prior impellers which have been and are being utilized in the food processing industry.
According to the inventors:
"The new impeller structure is not only a relatively low noise device, but its operation produces better results in size reducing a product than any impeller structure previously used. An important product used with the machine is meat and for this reason, meat will be referred to in describing the benefits of the new impeller. However, the new impeller is an improved device for the size reduction of many products such as, for example, horseradish, nuts, cheese, animal by products (used in pet foods), citrus peel, fresh corn (used for making canned or frozen cream style corn), field corn (for making corn mass for Mexican style foods), dehydrated potatoes (for producing potato flour), fish, rubber, coconut, sorghum, tomatoes, peppers, apricots, cranberries and pickles.
The following describes the problems experienced with various types of impellers: For use with most products to be size reduced, impeller speeds generally range between 3,600 and 6,500 RPM (revolutions per minute). The inside diameter of cutting heads or cylinders as presently used is six inches. With an impeller speed of 3,600 RPM, the centrifugal force is 1,105 gs. This means that a piece of meat rotating inside the cutting head at this speed is forced against the wall of the cutting head with a pressure of 1,105 times the weight of the piece of meat. Centrifugal force increases with the square of the speed and at 6,500 RPM, the centrifugal force is 3,602. This would make a piece of meat press against the wall of the cutting head with a pressure of 3,602 times the weight of the piece of meat.
FIG. 1 illustrates what may be referred to as a straight blade impeller 60 and FIG. 2 illustrates what happens to meat when being pushed or driven around inside a cutting head 61 by the straight blade impeller of FIG. 1. A combination of the centrifugal force and the force required to push the meat over the inside wall of the cutting head causes the meat to become semiliquid so that it spreads out over the entire surface of the impeller blade. This results in pressure at both the upper and lower ends of the impeller blades 62. Some of the meat is forced between the upper ends of the moving impeller blades and a stationary retaining plate. This friction tends to heat, cook and burn the meat as indicated at 63. This same condition exists at the lower ends of the impeller blades when meat is forced between the moving surface of the outside diameter of the bottom plate and a stationary surface of the head. If small amounts of meat are fed to the machine, the meat is cut quickly and discharged quickly, and the condition of overheating the meat is not serious. The condition becomes serious when large amounts of meat are fed to the machine and this thereby limits the value of the equipment. The noise produced by the straight blade impeller is a serious matter to the extent that this type of impeller is seldom used.
FIG. 3 illustrates what may be referred to as a slope forward impeller 70 and is depicted in FIG. 5 of a Joe R. Urschel U.S. Pat. No. 3,823,880 which issued on July 16, 1974, and a FIG. 4 related to FIG. 3 depicting what happens to the meat in the impeller. The pressure required to force the meat around inside a cutting head 71 causes the meat to slide downward along the surface of the impeller blades 72 and press against the bottom plate or base 73 of the impeller. The pressure becomes so great that some of the meat is forced between the moving outside diameter of the bottom plate of the impeller and the stationary surface of the cutting head. This causes heating, cooking and burning of the meat as indicated at 74. This condition is not too serious when small amounts of meat are fed to the machine but becomes serious when attempting to use the full capacity of the machine.
FIG. 5 depicts what may be defined as a slope backward impeller 80 which is also illustrated in FIG. 7 of the Urschel U.S. Pat. No. 3,823,880 referred to in the preceding paragraph and FIG. 6 related to FIG. 5 shows blades having product engaging surfaces which slope or are inclined rearwardly. In this case, the meat is forced upward and over the top of the moving impeller blades 81. The friction between these and the stationary retaining plate relative to a cutter head 82 causes the meat to heat, cook and burn as indicated at 83. This impeller is useful when feeding small amounts of meat to the machine but can not be used when feeding meat at the full capacity of the machine.
FIG. 7 illustrates what we call a "dogleg" impeller 80, and FIG. 8 relates to FIG. 7, with notations depicting its operation. The "dogleg" impeller may be considered to be a combination of the structures of FIGS. 3 and 4 and FIGS. 4 and 5 alluded to above. More specifically, the lower half of each impeller blade 91 is a slope backward impeller blade, and the upper half of each impeller blade is a slope forward impeller blade. This could also be called a V type impeller. This is the impeller type that consumes most of the manufacturing effort today. Up to this time, it has proven to be the best impeller type. It has a low noise output and from this standpoint is acceptable by all users. The meat is maintained at the middle of each impeller blade as indicated at 92 so that there is no danger of heating, cooking and burning of the meat at the ends of the blades. There are, however, two serious disadvantages to using this impeller. The machine produces a better cut product if the meat can be distributed over the full length of the blade rather than to be bunched up in the middle of the blade. A more serious problem is that there is great wear half way up the cutting head with little or no wear at other parts of the head. There would be much more utilization of the cutting head if the full length of the head could be used.
The objectives of the invention, detailed illustrations of the impeller structure and its operative relationship to a cutting head or cylinder and claims will appear subsequently, suffice to state in a preliminary way in comparative relation to the foregoing impellers briefly described above that the new or improved impeller has proven to have outstanding advantages over any other type of impeller. The advantages of this impeller is that the noise produced is within acceptable limits, there is no opportunity for meat to press against stationary parts to heat and burn, and the entire length of the blades are used to distribute the meat evenly over the inside surface of the cutting head. This impeller is composed of four blades. It can be made with any even number of blades. Each alternate blade is sloped backward and the other blades are sloped forward. The sloped backward blades are shortened at the top end and the sloped forward blades are shortened at the bottom ends. When meat is being cut by a sloped backward blade, the meat will gradually slide upward until it reaches the end of the blade. Then the meat will slide over the top of the blade and be picked up by the top of a sloped forward blade. The meat will slide gradually downward until it reaches the end of this blade. Then the meat will slide under the bottom of the blade and be picked up by the sloped backward blade. This procedure will continue until the piece of meat has all been cut and discharged from the machine. When the idea of this impeller was conceived, it was believed that meat would follow this path. High speed moving pictures were made of the machine cutting meat. The pictures were taken at about 8,000 pictures per second and then projected at about 15 pictures per second. The theory was confirmed with the result of these pictures.:
In addition, attention is directed for reference purposes to a Joe R. Urschel U.S. Pat. No. 3,196,916 which issued on July 27, 1965, and one U.S. Pat. No. 3,255,646 which issued on June 14, 1966, both being directed to segmented cutting heads and another U.S. Pat. No. 3,989,196 which issued on Nov. 2, 1976 involving a one-piece cutting head or cylinder. These additional Patents, among other things, serve to show the operative relationships between tubular cylindrical cutting heads and impeller structures for comminuting or reducing the size of various products or materials and copies of all Patents referred to in this application are attached and made a part of the record.